This invention relates to a broadband television network, and particularly a cable television system.
In many cable television systems, one or more television channels are dedicated to providing program information, local community information, and/or advertising (such as homes for sale). One channel that is commonly used for transmitting program information is the Prevue Channel, a commercial service that is available from Prevue Networks, Inc. of Tulsa, Okla. On the Prevue Channel, a cable company broadcasts a scrolling calendar of television shows on half of the television screen and advertising on the other half of the screen. With this service, a viewer must wait as long as four minutes for a schedule to scroll through a cycle of programs, and a user has no control over what or how program information is displayed.
Current set top boxes, such as the 8600.sup.x Home Communications Terminal produced by Scientific Atlanta, Inc. of Norcross, Ga., have significant memory, e.g., 256 kB, for storing an application program and for storing other data for display. This home terminal is discussed, for example, in Banker, U.S. Pat. No. 5,485,221, which shows a block diagram of a set top box. When the user selects a menu button on a remote control, the set top box causes menus to be displayed. These menus have options that can be selected by the user with the remote.
A primary feature is an on-screen electronic program guide (EPG) that is similar in appearance to those found in newspapers in that it has columns of times and rows of channels with cells that identify programs. Using the remote control, a user can traverse these rows and columns. When a user selects a cell, the system switches directly to the program identified in the cell.
The memory in the set top box stores the application program that runs the system, the EPG, and other information for display as shown in FIG. 5 of the Banker patent. When the user selects a menu selection, the application program retrieves data stored in memory. The set top box therefore has memory for storing all the information for display, and therefore the amount of information that can be transmitted to the user is limited by the size of the memory.
The set top box is in a stand-by mode when it is not actively turned on. Updates are made to the data in memory after the set top box is turned off and thus put in the stand-by mode, and when the set top box is turned on again. This means, however, that there are no updates if the set top box is not turned off to the stand-by mode.
Another currently used set top box is the model CFT 2200 from General Instrument. This particular model uses a separate part of the spectrum for "out of band" transmission at a relatively low frequency (compared to the VHF channels) at a rate of about 14.2 kb/sec. This set box top also holds an entire program guide and other information in memory in the set top box.